Linux SCSI driver development and usage

James.Smart | 1 Aug 2008 02:35

RE: [PATCH 1/2] scsi:netlink support in scsi and fc transports for hbaspecific messages

David Somayajulu wrote:
> > I'm a little bothered that there's nothing that qualifies the driver
> > to the shost before invoking the LLDD handler (e.g. driver has a
> > signature, message header contains signature, and the two 
> must match).
> The idea was to let the Low Level Driver validate the message 
> contents -
> signature, etc.

But that's the point - if we have a common action and a common point,
lets
do it once. Why have all LLDs perform the same kind of thing but in
completely different manners ? And worse, what happens if one doesn't
validate ?  The check doesn't have to be extensive, and the LLD
can certainly do more checks.

> I would appreciate if you can explain your comment a bit more, if my
> reasoning below does not suffice. I have already provided a function
> "fc_host_post_vendor_event_to_pid() [in 
> scsi_transport_fc.c]", which enables
> an LLD to post a message to a specific pid. This may be used 
> by the LLD to
> send response messages to the pid, for command messages sent 
> by the pid. 

it's not about sending...

What happens if the pid unexpectedly dies ? The event notices are an
easy way to find out that it died - thus releasing the "cached pid", or

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David Somayajulu | 1 Aug 2008 20:03

Re: [PATCH 1/2] scsi:netlink support in scsi and fc transports for hbaspecific messages


On 7/31/08 5:35 PM, "James.Smart <at> Emulex.Com" <James.Smart <at> Emulex.Com> wrote:

>  
> 
> David Somayajulu wrote:
>>> I'm a little bothered that there's nothing that qualifies the driver
>>> to the shost before invoking the LLDD handler (e.g. driver has a
>>> signature, message header contains signature, and the two
>> must match).
>> The idea was to let the Low Level Driver validate the message
>> contents -
>> signature, etc.
> 
> But that's the point - if we have a common action and a common point,
> lets
> do it once. Why have all LLDs perform the same kind of thing but in
> completely different manners ? And worse, what happens if one doesn't
> validate ?  The check doesn't have to be extensive, and the LLD
> can certainly do more checks.
In that case is it o.k to have the first 4 bytes of the LLD payload (i.e.,
following struct scsi_nl_hdr) define a signature. Let us also define the
signature to be the first 4 bytes in shost->hostt->name. This we can still
have some validation without much overhead.
> 
>> I would appreciate if you can explain your comment a bit more, if my
>> reasoning below does not suffice. I have already provided a function
>> "fc_host_post_vendor_event_to_pid() [in
>> scsi_transport_fc.c]", which enables
>> an LLD to post a message to a specific pid. This may be used

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